aio-libs aiohttp up to 3.13.3 Control Character response splitting

CVSS Meta Temp Score
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CTI Interest Score
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5.1$0-$5k0.00

Summaryinfo

A vulnerability described as problematic has been identified in aio-libs aiohttp up to 3.13.3. Affected by this vulnerability is an unknown functionality of the component Control Character Handler. Executing a manipulation can lead to response splitting. This vulnerability is tracked as CVE-2026-34520. The attack can be launched remotely. No exploit exists. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability classified as problematic was found in aio-libs aiohttp up to 3.13.3. This vulnerability affects an unknown code block of the component Control Character Handler. The manipulation with an unknown input leads to a response splitting vulnerability. The CWE definition for the vulnerability is CWE-113. The product receives data from an HTTP agent/component (e.g., web server, proxy, browser, etc.), but it does not neutralize or incorrectly neutralizes CR and LF characters before the data is included in outgoing HTTP headers. As an impact it is known to affect integrity. CVE summarizes:

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, the C parser (the default for most installs) accepted null bytes and control characters in response headers. This issue has been patched in version 3.13.4.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-34520 since 03/30/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are neither technical details nor an exploit publicly available.

Upgrading to version 3.13.4 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch 9370b9714a7a56003cacd31a9b4ae16eab109ba4 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

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Version

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Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA CVSS-B Score: 🔒
CNA CVSS-BT Score: 🔒
CNA Vector: 🔒

CVSSv3info

VulDB Meta Base Score: 5.3
VulDB Meta Temp Score: 5.1

VulDB Base Score: 5.3
VulDB Temp Score: 5.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Response splitting
CWE: CWE-113 / CWE-93 / CWE-74
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: aiohttp 3.13.4
Patch: 9370b9714a7a56003cacd31a9b4ae16eab109ba4

Timelineinfo

03/30/2026 CVE reserved
04/02/2026 +3 days Advisory disclosed
04/02/2026 +0 days VulDB entry created
04/02/2026 +0 days VulDB entry last update

Sourcesinfo

Product: github.com

Advisory: GHSA-63hf-3vf5-4wqf
Status: Confirmed

CVE: CVE-2026-34520 (🔒)
GCVE (CVE): GCVE-0-2026-34520
GCVE (VulDB): GCVE-100-354772

Entryinfo

Created: 04/02/2026 02:33
Changes: 04/02/2026 02:33 (71)
Complete: 🔍
Cache ID: 216:682:103

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